1. Field of the Invention
The present invention relates to a multimedia device, and more particularly, to an apparatus of a multimedia device with a multimedia interface for generating an audio clock.
2. Description of the Prior Art
In high definition multimedia interface (HDMI), video data and audio data are transmitted simultaneously using transition minimized differential signaling (TMDS). According to the HDMI specification, only a video frequency is directly transmitted via the cable. However, an audio clock is indirectly obtained through a first parameter N, and a second parameter CTS, both of which are recorded in an audio information frame, and the video frequency. According to the method described in the HDMI specification, the first parameter N, the second parameter CTS, the video frequency FV and an audio sampling frequency FA satisfy the following equation:
            1              (                  128          ×                      F            A                          )              ×    N    =      CTS    ×          1              F        V            
The quality of the generated audio clock is not good because the video clock itself may have jitter, or the video clock may be interfered by other noise signals during a data transmission process. In addition, both the first parameter N and the second parameter CTS are very large, so the PLL of the receiver for the audio clock needs components with high sensitivity implemented in the circuit design. Due to the above reasons, the conventional method for generating the audio clock has practical difficulties and restrictions.